Intestinal damage is required for the pro-inflammatory differentiation of commensal CBir1-specific T cells.

Commensal-specific clusters of differentiation (CD)4+ T cells are expanded in patients with inflammatory bowel disease (IBD) compared to healthy individuals. How and where commensal-specific CD4+ T cells get activated is yet to be fully understood. We used CBir1 TCR-transgenic CD4+ T cells, specific to a commensal bacterial antigen, and different mouse models of IBD to characterize the dynamics of commensal-specific CD4+ T-cells activation. We found that CBir1 T cells proliferate following intestinal damage and cognate antigen presentation is mediated by CD11c+ cells in the colon-draining mesenteric lymph nodes. Using assay for transposase-accessible chromatin sequencing and flow cytometry, we showed that activated CBir1 T cells preferentially acquire an effector rather than regulatory phenotype, which is plastic over time. Moreover, CBir1 T cells, while insufficient to initiate intestinal inflammation, contributed to worse disease outcomes in the presence of other CD4+ T cells. Our results suggest that the commensal-specific T-cell responses observed in IBD exacerbate rather than initiate disease.

Dietary environmental factors shape the immune defense against Cryptosporidium infection.

Cryptosporidium is a leading cause of diarrheal-related deaths in children, especially in resource-poor settings. It also targets the immunocompromised, chronically infecting people living with HIV and primary immunodeficiencies. There is no vaccine or effective treatment. Although it is known from human cases and animal models that CD4+ T cells play a role in curbing Cryptosporidium, the role of CD8+ T cells remains to be defined. Using a Cryptosporidium tyzzeri mouse model, we show that gut-resident CD8+ intraepithelial lymphocytes (IELs) confer resistance to parasite growth. CD8+ IELs express and depend on the ligand-dependent transcription factor aryl hydrocarbon receptor (AHR). AHR deficiency reduces CD8+ IELs, decreases their cytotoxicity, and worsens infection. Transfer of CD8+ IELs rescues severely immunodeficient mice from death following Cryptosporidium challenge. Finally, dietary supplementation of the AHR pro-ligand indole-3-carbinol in newborn mice promotes resistance to infection. Therefore, common dietary metabolites augment the host immune response to cryptosporidiosis, protecting against disease.

Interleukin-10 regulates goblet cell numbers through Notch signaling in the developing zebrafish intestine.

Cytokines are immunomodulatory proteins that orchestrate cellular networks in health and disease. Among these, interleukin (IL)-10 is critical for the establishment of intestinal homeostasis, as mutations in components of the IL-10 signaling pathway result in spontaneous colitis. Whether IL-10 plays other than immunomodulatory roles in the intestines is poorly understood. Here, we report that il10, il10ra, and il10rb are expressed in the zebrafish developing intestine as early as 3 days post fertilization. CRISPR/Cas9-generated il10-deficient zebrafish larvae showed an increased expression of pro-inflammatory genes and an increased number of intestinal goblet cells compared to WT larvae. Mechanistically, Il10 promotes Notch signaling in zebrafish intestinal epithelial cells, which in turn restricts goblet cell expansion. Using murine organoids, we showed that IL-10 modulates goblet cell frequencies in mammals, suggesting conservation across species. This study demonstrates a previously unappreciated IL-10-Notch axis regulating goblet cell homeostasis in the developing zebrafish intestine and may help explain the disease severity of IL-10 deficiency in the intestines of mammals.

The spatial transcriptomic landscape of the healing mouse intestine following damage.

The intestinal barrier is composed of a complex cell network defining highly compartmentalized and specialized structures. Here, we use spatial transcriptomics to define how the transcriptomic landscape is spatially organized in the steady state and healing murine colon. At steady state conditions, we demonstrate a previously unappreciated molecular regionalization of the colon, which dramatically changes during mucosal healing. Here, we identified spatially-organized transcriptional programs defining compartmentalized mucosal healing, and regions with dominant wired pathways. Furthermore, we showed that decreased p53 activation defined areas with increased presence of proliferating epithelial stem cells. Finally, we mapped transcriptomics modules associated with human diseases demonstrating the translational potential of our dataset. Overall, we provide a publicly available resource defining principles of transcriptomic regionalization of the colon during mucosal healing and a framework to develop and progress further hypotheses.

Perfluorooctanesulfonic acid modulates barrier function and systemic T-cell homeostasis during intestinal inflammation.

The intestinal epithelium is continuously exposed to deleterious environmental factors that might cause aberrant immune responses leading to inflammatory disorders. However, what environmental factors might contribute to disease are poorly understood. Here, to overcome the lack of in vivo models suitable for screening of environmental factors, we used zebrafish reporters of intestinal inflammation. Using zebrafish, we interrogated the immunomodulatory effects of polyfluoroalkyl substances, which have been positively associated with ulcerative colitis incidence. Exposure to perfluorooctanesulfonic acid (PFOS) during 2,4,6-trinitro-benzene sulfonic acid (TNBS)-induced inflammation enhanced the expression of proinflammatory cytokines as well as neutrophil recruitment to the intestine of zebrafish larvae, which was validated in the TNBS-induced colitis mouse model. Moreover, PFOS exposure in mice undergoing colitis resulted in neutrophil-dependent increased intestinal permeability and enhanced PFOS translocation into the circulation. This was associated with a neutrophil-dependent expansion of systemic CD4+ T cells. Thus, our results indicate that PFOS worsens inflammation-induced intestinal damage with disruption of T-cell homeostasis beyond the gut and provides a novel in vivo toolbox to screen for pollutants affecting intestinal homeostasis.

Lysophosphatidic Acid-Mediated GPR35 Signaling in CX3CR1+ Macrophages Regulates Intestinal Homeostasis.

Single-nucleotide polymorphisms in the gene encoding G protein-coupled receptor 35 (GPR35) are associated with increased risk of inflammatory bowel disease. However, the mechanisms by which GPR35 modulates intestinal immune homeostasis remain undefined. Here, integrating zebrafish and mouse experimental models, we demonstrate that intestinal Gpr35 expression is microbiota dependent and enhanced upon inflammation. Moreover, murine GPR35+ colonic macrophages are characterized by enhanced production of pro-inflammatory cytokines. We identify lysophosphatidic acid (LPA) as a potential endogenous ligand produced during intestinal inflammation, acting through GPR35 to induce tumor necrosis factor (Tnf) expression in macrophages. Mice lacking Gpr35 in CX3CR1+ macrophages aggravate colitis when exposed to dextran sodium sulfate, which is associated with decreased transcript levels of the corticosterone-generating gene Cyp11b1 and macrophage-derived Tnf. Administration of TNF in these mice restores Cyp11b1 expression and intestinal corticosterone production and ameliorates DSS-induced colitis. Our findings indicate that LPA signals through GPR35 in CX3CR1+ macrophages to maintain TNF-mediated intestinal homeostasis.

Retinoic acid induced cytokines are selectively modulated by liver X receptor activation in zebrafish.

Nuclear receptors (NRs) rapidly activate/repress gene expression to detour immune responses and allow tissue adaptation to constant environmental changes. However, the effect of combined NRs in the immune system is often unclear due to the lack of reliable experimental models that recapitulate the complex interaction between NRs in vivo. Here, we used the zebrafish to investigate the immunological outcome of combining the activation of retinoic acid receptor (RAR), liver X receptor (LXR) and the cytoplasmic sensor aryl hydrocarbon receptor (AHR). Although simultaneous activation did not affect the expression of respective bona-fide target genes, RAR-induced il17a/f3 was antagonized by LXR and AHR, whereas il22 was antagonized by AHR but not LXR. In addition, RA decreased il10 expression, which was further decreased by LXR activation. Thus, using combinatorial NR activation in zebrafish larvae, we show that LXR antagonizes the expression of selected RA-induced cytokines and provide a strategy to tailor the cytokine milieu.

Conserved transcriptomic profile between mouse and human colitis allows unsupervised patient stratification.

Clinical manifestations and response to therapies in ulcerative colitis (UC) are heterogeneous, yet patient classification criteria for tailored therapies are currently lacking. Here, we present an unsupervised molecular classification of UC patients, concordant with response to therapy in independent retrospective cohorts. We show that classical clustering of UC patient tissue transcriptomic data sets does not identify clinically relevant profiles, likely due to associated covariates. To overcome this, we compare cross-sectional human data sets with a newly generated longitudinal transcriptome profile of murine DSS-induced colitis. We show that the majority of colitis risk-associated gene expression peaks during the inflammatory rather than the recovery phase. Moreover, we achieve UC patient clustering into two distinct transcriptomic profiles, differing in neutrophil-related gene activation. Notably, 87% of patients in UC1 cluster are unresponsive to two most widely used biological therapies. These results demonstrate that cross-species comparison enables stratification of patients undistinguishable by other molecular approaches.

Reproductive and Behavior Dysfunction Induced by Maternal Androgen Exposure and Obesity Is Likely Not Gut Microbiome-Mediated.

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disorder of unclear etiology in women and is characterized by androgen excess, insulin resistance, and mood disorders. The gut microbiome is known to influence conditions closely related with PCOS, and several recent studies have observed changes in the stool microbiome of women with PCOS. The mechanism by which the gut microbiome interacts with PCOS is still unknown. We used a mouse model to investigate if diet-induced maternal obesity and maternal DHT exposure, mimicking the lean and obese PCOS women, cause lasting changes in the gut microbiome of offspring. Fecal microbiome profiles were assessed using Illumina paired-end sequencing of 16S rRNA gene V4 amplicons. We found sex-specific effects of maternal and offspring diet, and maternal DHT exposure on fecal bacterial richness and taxonomic composition. Female offspring exposed to maternal obesity and DHT displayed reproductive dysfunction and anxietylike behavior. Fecal microbiota transplantation from DHT and diet-induced obesity exposed female offspring to wild-type mice did not transfer reproductive dysfunction and did not cause the expected increase in anxietylike behavior in recipients. Maternal obesity and androgen exposure affect the gut microbiome of offspring, but the disrupted estrous cycles and anxietylike behavior are likely not microbiome-mediated.